1. Field of the Invention
The invention relates to the headrest support structure of a seat installed in a conveyance.
2. Description of Related Art
A headrest of an automobile seat is formed in such a way that right and left headrest stays annexed to the headrest are fixed to an upper frame as part of a seat back structure. Specifically, a pair of cylindrical headrest holders fits in the first and second pairs of fitting holes of the upper frame to be fixed, headrest supports fit in the respective headrest holders, and the headrest stays are fixed to the respective headrest supports so as to be movable vertically. A locking mechanism is provided between one of the headrest supports and one of the headrest stays to allow the adjustment of the vertical position of the headrest stays with respect to the headrest supports, i.e., the height of the headrest. U.S. Pat. No. 5,788,250 describes an example of such a headrest support structure of an automobile seat.
Since only one of the right and left headrest supports is provided with the locking mechanism as described above, the left headrest support and the right headrest support are different in structure from each other. In addition, in order to correctly assemble the headrest supports into the headrest holders without confusing their right and left sides, the left headrest holder and the right headrest holder are different in shape from each other. Moreover, in order to correctly assemble the headrest holders into the upper frame without confusing their right and left sides, a special jig is used to insert the headrest holders in the fitting holes of the upper frame.